A marine escape system is used for evacuating people from a structure at sea in the event of an emergency. Such a structure may be an oil rig or a ship.
One form of marine escape system includes liferafts into which the people are evacuated. Since, when liferafts are deployed on water, there is usually a significant difference in height (freeboard) between the point on the structure from which the people are evacuated and the liferafts, it is necessary to provide some form of passage between the two.
It is known to provide an angled chute, which may be formed from inflatable members, extending between the evacuation point and the liferafts. The chute can extend either direct to the liferafts or to an inflatable floating structure to which the liferafts are attached. In some vessels, the freeboard may be 14-15 meters and so the chute is of significant length.
Recent sinkings of ships have placed greater emphasis on the need to evacuate marine structures quickly in the event of an emergency. It is likely to be a requirement that any seagoing vessel must be able to evacuate 400 people in 17 minutes 40 seconds. In addition, it is likely to be a requirement that any marine escape system must be able to operate in force six weather which will include a 3 meter swell and that the marine escape system must be usable for a considerable period of time with the vessel side-on to the sea.
An angled chute is not readily able to meet such a requirement. Since the chute projects from the side of a vessel it requires stabilization in order to prevent significant lateral movements in heavy weather. Further, to accommodate such weather, the chute must be comparatively rigid and this can increase significantly the bulk of the chute.
Marine escape systems have also been proposed in which the connection between the evacuation point and the inflatable L liferafts is via a tube containing a helical slide passage. A person entering the passage at the escape point travels in a helical path along the passage and emerges at an exit at the lower end of the tube.
A tube requires less stabilization than a chute against lateral movement in heavy weather. However, the tube has the problem of accommodating swell which, as mentioned above, may alter the freeboard of a vessel by six or more meters.
It has previously been proposed to accommodate this by making the tube of flexible material with a maximum length sufficient to accommodate the swell. The tube hangs from the evacuation point on the structure and has excess length heaped on a platform to which people are evacuated when the swell is less than the maximum. As the space in between the platform and the evacuation point varies, more or less of the tube is either extended from or piled into the heap on the platform. It is a problem with such an arrangement that no single exit can be provided. In order to overcome this problem, such tubes have previously been provided with a plurality of exits spaced along their length; with evacuated persons emerging from the exit closest to the platform at the time they reach the platform. This is not, however, satisfactory because a person may exit too soon or the position of the platform may change to make a selected exit suddenly inappropriate.
According to the invention, there is provided a marine escape system comprising a passage for persons and having an entrance at one end and an exit at an end opposite said one end, at least one support for the passage being provided between the entrance and the exit, the support being suspended by at least one first elongate elastic member, at least one second elongate elastic member extending from the support towards the exit, the at least one second elongate elastic member having a greater elasticity, than the at least one first elongate elastic member, so that a portion of the passage between the exit and the support is extensible and contractible before the extension and contraction of a portion of the passage between the entrance the support, the passage being extensible and contractible to accommodate changes in the spacing between the entrance and the exit.
By varying the length of the tube between the entrance and the exit, a swell can be accommodated while maintaining a single exit.
According to a second aspect of the invention, there is provided an escape chute comprising an elongate tube which is deployed generally vertically and a succession of spaced members within the tube and defining, with the tube, a path for the passage of a person through the tube.